This invention generally relates to air temperature control in aircraft cabins, for example. More particularly, this invention relates to a strategy for controlling temperature in a vehicle cabin by cooling recirculated air.
Aircraft and other vehicles include cabin temperature control systems that provide a desired air temperature within the cabin. In the case of aircraft, the cabin is pressurized and the pressurized air is brought close to a desired temperature so that individuals within the cabin remain comfortable. A variety of cabin air temperature control systems are known.
One challenge facing designers of such systems is achieving optimum system performance while staying within the limitations on power consumption and packaging, which are typically imposed by the nature of aircraft or other vehicles. Minimizing the use of power is important so that power source size and expense, fuel consumption or both are kept within acceptable, economical levels. Space also typically is limited and packaging such a system must fit within tight guidelines.
Typical aircraft cabin air conditioning systems include an air cycle machine that utilizes outside air, conditions the outside air to bring the temperature of such air closer to a desired cabin temperature and then introduces the conditioned air into the cabin. Such systems also typically include recirculation of the cabin air. The recirculated cabin air typically is not conditioned (not cooled or not heated), but rather is simply recirculated. The recirculated air sometimes is mixed with the conditioned air so that a mixture of the recirculated air and the conditioned air is introduced into the cabin.
One drawback associated with typical arrangements is that desired temperature levels are not always readily achieved. For example, on warm days when an aircraft is on the ground, the system is not capable of adequately cooling air to keep the cabin at a comfortable temperature level. It is desirable to increase the cooling capacity of a cabin air temperature control system without increasing power consumption or drastically changing the configuration of the system so that the system stays within industry recognized packaging constraints.
This invention provides a unique solution to the problem of achieving adequate temperature control of cabin air without requiring additional power consumption compared to conventional arrangements.
In general terms, this invention is a cabin air temperature control system that includes selectively cooling recirculated cabin air before the recirculated air is reintroduced into the cabin.
A system designed according to this invention includes a first air flow circuit having an inlet that receives air from outside of the cabin. An air conditioner assembly adjusts the temperature of the outside air to bring it closer to a desired cabin temperature. The conditioned air is then introduced into the cabin. A second air flow circuit recirculates air from the cabin back into the cabin. A recirculation air cooling assembly is provided in the second circuit to selectively cool the recirculated air before it is reintroduced into the cabin.
In one example, the recirculated air cooling assembly comprises a heat exchanger.
Under circumstances where it is not necessary or desirable to cool the recirculated air, a bypass flow pathway is utilized to direct the recirculated air back into the cabin without cooling it. A temperature sensor and a controller communicate so that the controller can determine whether the recirculated air should be cooled based upon a currently desired cabin temperature and a current recirculated air temperature. The controller preferably controls an air flow control device to direct the recirculated air through the recirculating air cooling assembly or, alternatively, through the bypass so that the recirculated air is not cooled.
The recirculated air preferably is mixed with the conditioned air from the first circuit so that a mixture of the conditioned air and the recirculated air is introduced into the cabin.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawing that accompanies the detailed description can be briefly described as follows.